I had unprotected sex a week before my period, and he might've pre-ejaculated. are my chances of getting pregnant high? should i take plan b?

0 Risk During Period: If you already had a period then it's highly unlikely for you to have gotten pregnant. Any egg would be flushed from your uterus along with the uterine lining and so no worries. But if you have not had a period yet and are expecting one and it's been less than three days since sex, then you should get Plan B and then some birth control! Make sure you're not already pregnant.

Possible: Most fertile time is 14 days before the period. So risk is not that high. How long ago was sex? Plan B One-Step is up to 89 % effective when taken within 72 hours (3 days) after unprotected sex. It can reduce chance of pregnancy by up to 95% if used within 24 hours. Pre-ejaculate may contain large amounts of viable sperm (less common), smaller amounts of sperm that are dead or alive or no sperm.